Origin

You could not eat a pea until the mid 17th century. The earlier form was pease, which people began to think was a plural, so that if you had a handful of peas you must be able to have one pea ( compare cherry). The original is recorded in Old English, and goes back to Greek pison; it survives in pease pudding, for boiled split peas mashed to a pulp. The pea of peacock has no connection—it derives from Latin pavo ‘peacock’, which appears as pea in Old English and was combined with cock ‘male bird’ in Middle English. Nor does a pea jacket have anything to do with peas. It is an early 18th-century half-hearted translation of Dutch pijjackker formed from pij ‘coarse woollen cloth’ (found in Middle English as pee) and jekker ‘jacket’.